Validate telephone numbers.

Closes: https://github.com/Karaage-Cluster/karaage/issues/191

Required format is set by RFC2252 section 6.30 which refers to E.123
http://www.itu.int/rec/T-REC-E.123-200102-I/en

Change-Id: Ie8050ae032420ce58e1fb97a37442c3e2169cd46